This invention relates to a copper alloy which is suitable as a material which must have general properties such as heat resistance, electric and heat conductivity, solderability, workability and mechanical strength, including a material for semiconductor lead frames, a material for electronic and electrical parts such as connector switches, or a material for heat exchanger fins.
As a lead frame material for electronic devices such as semiconductors, IC, and LSI, 42-alloy (Fe-42% Ni alloy) having good sealability for a ceramic package has heretofore been used generally. As resin packaging becomes widespread recently and its cost is reduced, the use of lead frame materials of a copper alloy has been increased rapidly, and CDA 194 alloy and phosphor bronze are chiefly used. Recently, with the progress of large IC integration, a demand has grown for high-strength, highly heat-resistant copper alloys. The above-mentioned CDA 194 alloy, however, has a somewhat lower softening temperature though it has good strength and conductivity (heat conductivity can be roughly estimated from electric conductivity), whereas phosphor bronze has a lower conductivity though it has excellent strength and flexibility. Thus, they have both merits and demerits.
The properties which a material for lead frames must generally have are as follows:
(1) A lead frame material has excellent electric and heat conductivity corresponding to the degree of integration of a semiconductor. PA1 (2) A lead frame material can withstand high temperatures during die bonding and is resistant to softening. PA1 (3) Its lead portion can withstand bending and has an excellent strength sufficient to resist twisting and bending by a stress exerted on the lead portion when its thickness is reduced. PA1 (4) A lead frame material has good solderability. PA1 (5) A lead frame material has good oxidation resistance at high temperatures. PA1 (6) A lead frame material undergoes no hydrogen embrittlement.
On the other hand, with regard to copper alloys for use in electrical parts such as connector switches, heretofore known excellence in their properties such as conductivity, stress corrosion cracking resistance, and corrosion resistance will not suffice, and it is desirable in reducing the cost by thinning the parts that the copper alloys have sufficient strength and excellent heat resistance during brazing.
Also the properties of Sn-containing copper (Cu-0.2% Sn) which has heretofore been used as main material for heat exchanger fins cannot cope with the tendency of the reduction in the thickness of a material. Therefore, there has been a demand for copper alloys which have excellent mechanical strength and softening resistance as well as sufficient conductivity.
Announced copper alloys having improved mechanical strength and conductivity include a Cu-Fe-Ti-Ni quaternary alloy having a composition of 1.4% of Fe, 1.0% of Ti, 1.5% of Ni, and the balance of Cu (Japanese Patent Publication No. 1253/1959) and a Cu-Fe-Mg-P quaternary alloy (U.S. Pat. No. 4,305,762). According to the confirmative study by the inventors of this invention, however, they can not be said to be fully satisfactory in respect of the properties which are required of, for example, a material for lead frames, especially electric conductivity and mechanical strength.
In view of these facts, this invention has been made for the purpose of facilitating the industrial production of a Cu-Fe-Ti ternary alloy excellent in strength, electric and heat conductivity and heat resistance and of improving its properties by adding additives.